Letters to the Editor / Cartas al Editor
THE CHICK CHORIOALLANTOIC MEMBRANE
Figure 2.- The cracked egg shell.
Figure 3.- The CAM of Hen’s fertile egg
The exposed CAM was divided into four parts 1, 2, 3 and 4. These were written on the four sides.The preparations were applied on these spots as a drop in the following manner: Area 1: Multipurpose solution coded as MPS-2. Area 2: Sodium lauryl sulphate (SLS). Area 3: Baby shampoo (Johnson). Area 4: Propylene glycol (PG)
Immediately, these were kept in the incubator and after 0.5, 2 and 5 minutes, the area were examined for hyperaemia, haemorrhage and coagulation. The resultant scores obtained were shown in table 3
The multipurpose solution coded as MPS-2 was formulated on pilot scale. The irritation studies on the preparation MPS-2 used as rinsing and soaking solution for hydrophilic contact lenses were performed using chorio allantoic membrane (CAM) test of fertile hen's egg. The preparation was applied as a drop on the CAM and scores for haemorrhage, hyperaemia and coagulation were observed and were recorded. The mean score was calculated and cumulative score was obtained. This was obtained as 0.50.As per the interpretation of standard parameter a cumulative score in between 0-0.9 is practically non-irritant. Therefore multipurpose solution MPS-2 was found to be practically non-irritant. For comparative purpose the test was also performed for propylene glycol, baby shampoo and sodium lauryl sulphate. For propylene glycol the cumulative score was 0.33 hence it is also nonirritant. This was practically observ.ed on CAM. A substance is slightly irritant if the mean score is in the range of 1-4.9. For sodium lauryl sulphate, the cumulative score was 10.99 hence it indicated a strong irritation effect as it was in the cumulative score range of 9-21. The three materials that were used. Propylene glycol, baby shampoo and SLS as controls in the study.
Irritation studies should be carried out on preparation like multipurpose solution because it has to be used for rinsing and soaking of CL's (hydrophilic contact lenses). The CAM is very much similar to retina of the eye hence can be used for irritation studies on eye preparations. Such experiments are less expensive and do not require extensive animal protocol. Maintenance of eggs requires adequate humidity and a 37°C environment and rotation after every few hours, which can be performed in an inexpensive incubator.
The type of CAM experiments described herein can optimally be performed between incubation days 12 and 18. Before day 12, the CAM vasculture has not adequately matured. After day 18, the embryo is large enough that its size and movements underneath the CAM can disrupt experimental maneuvers on the CAM, Additionally, standard animal protocols for chick embryos past 18 require more complicated euthanasia techniques.
Conclusion: The optimized product MPS-2 and marketed by the name of Multisol is practically non irritant and can be used for rinsing, soaking, disinfecting, lubricating and deproteinising hydrophilic contact lenses.
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Prof. Alka Arora PhD
3- B-264 Derawal Nagar, opp. Model Town-2 Delhi-110009, India.
mail alkamailin @ yahoo.co.in
Received reviewed, July 1, 2009.
Published, July 19, 2009